1. Field of the Invention
The present invention relates generally to a method and apparatus for the production of a cast component. More particularly, in one embodiment of the present invention, a focused (non-diffuse) energy source (e.g. a laser—although a laser does not necessarily need to be focused) is use to control the temperature gradient at the solidification interface during solidification of single crystal or directionally solidified castings. Another embodiment of the present invention is to control casting shrink during solidification of all types of castings (including equiaxed castings). Although one form of the invention is directed to producing single crystal or directionally solidified castings for gas turbine blades, the present invention also includes certain applications outside of that field.
2. Brief Description of Art
The performance of a gas turbine engine generally increases with an increase in the operating temperature of a high temperature working fluid flowing from a combustor. One factor recognized by gas turbine engine designers as limiting the allowable temperature of the working fluid is the capability of the engine components to not degrade when exposed to the high temperature working fluid. The components, such as blades and vanes, within the engine and downstream of the combustor are exposed to significant thermal and kinetic loading during engine operation. The repeated thermal and kinetic loading have caused mechanical failure of these engine components by creep and cracking. In recognition of the prior component failures and that the performance of these components ultimately dictate the engine performance, it has been generally accepted to make these components as single crystal or directionally solidified castings. Further, the demand for continued engine performance has resulted in the development of components having an internal network of apertures and passageways. Therefore, in modem advanced gas turbine engines many of the components are generally hollow air-cooled structures having a directionally solidified or single crystal microstructure.
Although there are well established techniques for producing directionally solidified and single crystal cast components with internal passageways and apertures there remains a need for a simpler, less expensive method and apparatus for casting these components. The present invention satisfies this and other needs in a novel and unobvious way.